The concept of constituent power emerges alongside that of the modern documentary constitution. It expresses the conviction that the authority of the constitution rests on its having been drafted in the name of ‘the people’ who, through an exercise of their constitution-making power, are the authors of that constitution. Conceiving the constitution as an expression of collective self-government, constituent power is therefore closely associated with the concept of popular sovereignty. This chapter examines how constituent power emerged in modern thought, explains its original meaning, sketches its subsequent evolution in thought, and evaluates the role it continues to play in contemporary constitutional discourse.

Does the absence of a legal rupture, the failure to put into practice the idea of a legally unrestrained popular sovereign, necessarily mean that an exercise of constituent power has not taken place? Can constituent power be exercised through law? These are questions that indirectly challenge one of the features normally attributed to constituent power: its unmediated and uncontrollable nature. This chapter will compare two traditions of constitutional thought (that of Sieyès and Rousseau) that provided different answers to those questions and explore the ways in which the idea that constituent power can be exercised through legally recognised procedures has figured in later constitutional theory and practice.